The anti-pollution standards generally associate a given constraint with each type of pollutant emitted by the engine (including noise).
When these standards are not too severe, it is possible to find different control methods that make it possible, for a given torque and engine speed, to satisfy these standards. It is in particular possible to find a control mode which, on the one hand, satisfies these standards, and, on the other hand, makes it possible to optimize the engine fuel consumption.
However, the standards associated with compression ignition engines (diesel) are particularly severe and require the architecture and the control systems of the internal combustion engines to be refined.
However, beyond a certain level of refinement, it is no longer possible to satisfy the anti-pollution standards by acting only on the architecture and the control systems of the engines. Also, it is necessary to provide post-treatment systems for the polluting elements (of particular filter type) to be able to find a compromise between pollutant emissions, noise and other constraints.
Simply, these post-treatment systems are costly to build, to maintain and to install in the motor vehicles. They are consequently engineered to the necessary minimum, so that the compromise between the different constraints still remains difficult to manage.
Currently, the constraints taken into account for controlling the engines are determined by considering the situation that is most unfavorable to the engine, and are therefore independent of the configuration in which the vehicles actually are (in town, on the motorway, etc.).
In the event, among the constraints currently taken into account and that make this compromise difficult to find, the charge rate of the particulate filter can be cited. It is in fact necessary to provide the possibility for regular regeneration, regardless of the configuration in which the vehicle is.
The configuration that is most unfavorable corresponds to successions of short and slow journies, during which the engine emits a lot of particulates which cannot be burnt since the exhaust line remains cold.
The known control methods are then set up according to these worst conditions, without checking whether the vehicle is actually in these worst conditions or in more favorable conditions. This type of setting is therefore not optimized, in particular with regard to engine fuel consumption.